(a) What minimum force F is required to prevent the block from sliding down the wall? (Hint: The static frictional force exerted on the block is directed upward, parallel to the wall.)
(b) What minimum force is required to start the block moving up the wall? (Hint: The static frictional force is now directed down the wall.)
12. 0/2 points All Submissions Notes
In the drawing, the weight of the block on the table is 474 N and that of the hanging block is 185 N. Ignore all frictional effects, and assume the pulley to be massless.
(a) Find the acceleration of the two blocks.
b) Find the tension in the cord
A cable is lifting a construction worker and a crate, as the drawing shows. The weights of the worker and crate are 951 and 1490 N, respectively. The acceleration of the cable is 0.620 m/s2, upward.
(a) What is the tension in the cable below the worker?
(b) What is the tension in the cable above the worker?
A box is sliding up an incline that makes an angle of 15.0° with respect to the horizontal. The coefficient of kinetic friction between the box and the surface of the incline is 0.180. The initial speed of the box at the bottom of the incline is 1.10 m/s. How far does the box travel along the incline before coming to rest?
A falling skydiver has a mass of 125 kg.
(a) What is the magnitude of the skydiver's acceleration when the upward force of air resistance has a magnitude that is equal to one-fourth of his weight?
(b) After the parachute opens, the skydiver descends at a constant velocity. What is the force of air resistance (magnitude and direction) that acts on the skydiver?
A rock of mass 33 kg accidentally breaks loose from the edge of a cliff and falls straight down. The magnitude of the air resistance that opposes its downward motion is 252 N. What is the magnitude of the acceleration of the rock?
A 92.0-kg person stands on a scale in an elevator. What is the apparent weight when the elevator is
(a) accelerating upward with an acceleration of 1.70 m/s2,
(b) moving upward at a constant speed, and
(c) accelerating downward with an acceleration of 1.20 m/s2?
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18. –/1 points Notes
The steel I-beam in the drawing has a weight of 7.00 kN and is being lifted at a constant velocity. What is the tension in each cable attached to its ends?
In a supermarket parking lot, an employee is pushing ten empty shopping carts, lined up in a straight line. The acceleration of the carts is 0.065 m/s2. The ground is level, and each cart has a mass of 24 kg.
(a) What is the net force acting on any one of the carts?
(b) Assuming friction is negligible, what is the force exerted by the fifth cart on the sixth cart?
From the top of a tall building, a gun is fired. The bullet leaves the gun at a speed of 340 m/s, parallel to the ground. As the drawing shows, the bullet puts a hole in a window of another building and hits the wall that faces the window. (y = 0.46 m, and x = 6.4 m.) Using the data in the drawing, determine the distances D and H, which locate the point where the gun was fired. Assume that the bullet does not slow down as it passes through the window.
H = m
D = m
The drawing shows a large cube (mass = 35 kg) being accelerated across a horizontal frictionless surface by a horizontal force P. A small cube (mass = 2.2 kg) is in contact with the front surface of the large cube and will slide downward unless P is sufficiently large. The coefficient of static friction between the cubes is 0.71. What is the smallest magnitude that P can have in order to keep the small cube from sliding downward?